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Evaluation of Spent Coffee Obtained from the Most Common Coffeemakers as a Source of Hydrophilic Bioactive Compounds

The main hydrophilic antioxidant compounds (3-, 4-, and 5-monocaffeoylquinic and 3,4-, 3,5-, and 4,5-dicaffeoylquinic acids, caffeine, and browned compounds, including melanoidins) and the antioxidant capacity (Folin-Ciocalteu, ABTS, DPPH, Fremys salt, and TEMPO) were evaluated in Arabica and Robusta spent coffee obtained from the preparation of coffee brews with the most common coffeemakers (filter, espresso, plunger, and mocha). All spent coffee grounds, with the exception of those from the mocha coffeemaker, had relevant amounts of total caffeoylquinic acids (6.22-13.24 mg/g of spent coffee), mainly dicaffeoylquinic acids (3.31-5.79 mg/g of spent coffee), which were 4-7-fold higher than in their respective coffee brews. Caffeine ranged from 3.59 to 8.09 mg/g of spent coffee. The antioxidant capacities of the aqueous spent coffee extracts were 46.0-102.3% (filter), 59.2-85.6% (espresso), and <42% (plunger) in comparison to their respective coffee brews. This study obtained spent coffee extracts with antioxidant properties that can be used as a good source of hydrophilic bioactive compounds.

Influence of Brewing Method and Acidity Regulators on the Antioxidant Capacity of Coffee Brews

The antioxidant capacity of coffee brews prepared with different coffeemakers (filter, plunger, mocha, and espresso) was measured by colorimetric (total phenolic compounds and ABTS) and electron spin resonance (ESR) spectroscopy techniques (Fremys salt and TEMPO). The mocha coffeemaker had the highest yield in coffee antioxidant extraction per gram of ground roasted coffee, but espresso coffee was richest in terms of antioxidant intake (per milliliter of coffee brew) followed by mocha, plunger, and filter. Both Folin-Ciocalteu (total phenolic compounds) and ABTS assays reacted with standard solutions of chlorogenic acids (CGA) and melanoidins (MO-Ala and MO-Gly). However, Fremys salt was mainly scavenged by chlorogenic acids, whereas the stabilized radical TEMPO was effectively scavenged by melanoidins, but not by chlorogenic acids. Thus, ESR spectroscopy allows distinguishing between phenolic and nonphenolic antioxidants. Moreover, the addition of pH-regulator agents to coffee, such as sodium carbonate (75 ppm) and bicarbonate (75 ppm), to extend its shelf life, slightly increases the pH, modifying the antioxidant capacity in those coffee brews with the highest capacity (mocha and espresso).

Antioxidant and genoprotective effects of spent coffee extracts in human cells.

Spent coffee has been shown as a good source of hydrophilic antioxidant compounds. The ability of two spent coffee extracts rich in caffeoylquinic acids, mainly dicaffeoylquinic acids, and caffeine (Arabica filter and Robusta espresso) to protect against oxidation and DNA damage in human cells (HeLa) was evaluated at short (2 h) and long (24 h) exposure times. Cell viability (MTT) was not affected by spent coffee extracts (>80%) up to 1000 μg/mL after 2 h. Both spent coffee extracts significantly reduced the increase of ROS level and DNA strand breaks (29-73% protection by comet assay) induced by H₂O₂. Pretreatment of cells with robusta spent coffee extract also decreased Ro photosensitizer-induced oxidative DNA damage after 24 h exposure. The higher effectiveness of Robusta spent coffee extract, with less caffeoylquinic acids and melanoidins, might be due to other antioxidant compounds, such as caffeine and other Maillard reaction products. This work evidences the potential antioxidant and genoprotective properties of spent coffee in human cells.

Assessment of Total (Free and Bound) Phenolic Compounds in Spent Coffee Extracts

Spent coffee is the main byproduct of the brewing process and a potential source of bioactive compounds, mainly phenolic acids easily extracted with water. Free and bound caffeoylquinic (3-CQA, 4-CQA, 5-CQA), dicaffeoylquinic (3,4-diCQA, 3,5-diCQA, 4,5-diCQA), caffeic, ferulic, p-coumaric, sinapic, and 4-hydroxybenzoic acids were measured by HPLC, after the application of three treatments (alkaline, acid, saline) to spent coffee extracts. Around 2-fold higher content of total phenolics has been estimated in comparison to free compounds. Phenolic compounds with one or more caffeic acid molecules were approximately 54% linked to macromolecules such as melanoidins, mainly by noncovalent interactions (up to 81% of bound phenolic compounds). The rest of the quantitated phenolic acids were mainly attached to other structures by covalent bonds (62-97% of total bound compounds). Alkaline hydrolysis and saline treatment were suitable to estimate total bound and ionically bound phenolic acids, respectively, whereas acid hydrolysis is an inadequate method to quantitate coffee phenolic acids.

Influence of heat treatment on antioxidant capacity and (poly)phenolic compounds of selected vegetables.

The impact of cooking heat treatments (frying in olive oil, frying in sunflower oil and griddled) on the antioxidant capacity and (poly)phenolic compounds of onion, green pepper and cardoon, was evaluated. The main compounds were quercetin and isorhamnetin derivates in onion, quercetin and luteolin derivates in green pepper samples, and chlorogenic acids in cardoon. All heat treatments tended to increase the concentration of phenolic compounds in vegetables suggesting a thermal destruction of cell walls and sub cellular compartments during the cooking process that favor the release of these compounds. This increase, specially that observed for chlorogenic acids, was significantly correlated with an increase in the antioxidant capacity measured by DPPH (r=0.70). Griddled vegetables, because of the higher temperature applied during treatment in comparison with frying processes, showed the highest amounts of phenolic compounds with increments of 57.35%, 25.55% and 203.06% compared to raw onion, pepper and cardoon, respectively.

Application of multivariate analysis to the effects of additives on chemical and sensory quality of stored coffee brew.

The aim of this work was to obtain a black coffee brew to be consumed hot by extension of its shelf life, by addition of additives. Four pH-regulator agents (sodium and potassium carbonates and bicarbonates), one pH regulator and antioxidant (sodium citrate), three antioxidants [sodium ascorbate, ethylenediaminetetracetic acid (EDTA), and sodium sulfite], and lactoserum were tested by sensory analysis. Sodium carbonate and bicarbonate were selected for a study of the physicochemical (soluble and volatile compounds related to the sensory properties) and sensorial quality of coffee brew stored for 90 days at 4 degrees C. Although both additives extended the shelf life of the coffee brew up to 60 days, sodium carbonate was the chosen additive because it was the most useful in limiting the pH decrease and perception of sourness, which are some of the main factors involved in the rejection of stored coffee brews, and it better maintained the aroma and taste/flavor. Moreover, the application of multivariate analysis facilitated first the description of the global changes of the coffee brews with or without additives throughout the storage using principal component analysis and second the obtainment of a simple equation only with pH and caffeic acid parameters to discriminate the three types of coffee brews and simplify the analytical process, by means of the stepwise discriminant analysis.

In vitro studies on the stability in the proximal gastrointestinal tract and bioaccessibility in Caco-2 cells of chlorogenic acids from spent coffee grounds

Abstract Spent coffee grounds are a potential commercial source of substantial amounts of chlorogenic acids (CGAs). The aim of this study was to evaluate the stability of spent coffee CGAs using in vitro simulated gastroduodenal digestion and to investigate their potential absorption using an in vitro Caco-2 model of human small intestinal epithelium. During in vitro digestion, lactones were partially degraded while caffeoylquinic and feruloylquinic acids were much more stable. Transport and metabolism studies showed that 1% of the total CGAs were absorbed and transported from the apical to the basolateral side of a Caco-2 cell monolayer after 1 h. Lactones and coumaroylquinic acids showed the rate of highest absorption. Caco-2 cells possessed low metabolic activity. In conclusion, spent coffee extracts contain large amounts of CGAs, which remained bioaccessible across the intestinal barrier, albeit to a relatively low degree.

How Does Roasting Process Influence the Retention of Coffee Aroma Compounds by Lyophilized Coffee Extract

The aims of this study were (1) to study the effect of lyophilized coffee extract on the retention of aroma compounds and (2) to study if aroma compounds selected are differently affected by the lyophilized coffee extracts obtained from conventional and Torrefacto coffee brews prepared by filter coffeemaker and by espresso coffee machine. Variable amounts of lyophilized coffee extracts, relative to coffee powder, containing different percentages of high molecular weight compounds, mainly melanoidins (value given in parentheses), were obtained: 20.9% (14.8) and 24.9% (23.3), respectively, for conventional and Torrefacto coffee brew prepared by filter coffeemaker and 18.1% (18.8) and 20.7% (57.5), respectively, for conventional and Torrefacto coffee brew prepared by espresso coffee machine. The retention of aroma compounds increased by increasing the lyophilized coffee extract concentration and was found to be dependent on the aroma compounds. The retention of aroma compounds was found to be slightly different depending on the brewing procedure employed, showing lyophilized coffee extracts obtained with espresso coffee machine had higher retention values that those extracted by filter coffeemaker. Retention capacity of lyophilized coffee extracts obtained from the conventional and the Torrefacto roasted coffee did not show differences except in the case of ethyl nonanoate.

Impact of cooking process on nutritional composition and antioxidants of cactus cladodes (Opuntia ficus-indica)

The impact of cooking methods (boiling, microwaving, griddling and frying in olive and soybean oils) on nutritional composition (protein, minerals, fat, carbohydrates, fibre, fatty acid profile and energy), antioxidant capacity and (poly)phenolic compounds of cactus cladodes (Opuntia ficus-indica) was evaluated. Culinary processes, except boiling, increased soluble and insoluble fibre up to 5.0g/100g becoming a good fibre source. Cactus cladodes fried in olive oil showed a healthier fatty acid profile and lower ω-6/ω-3 ratio than in soybean oil. Flavonoids accounted for 80% of total (poly)phenolic compounds, being isorhamnetin the most abundant. Heat treatment, particularly griddling and microwaving, increased every flavonoid and phenolic acid up to 3.2-fold higher than in raw samples, and consequently their antioxidant capacity. Even boiling induced losses in total (poly)phenols and antioxidant capacity by leaching into water, the main compounds were maintained. Principal Component Analysis distributed heat treated cactus cladodes according to their distinctive polyphenols and antioxidant capacity.

Digestibility of (Poly)phenols and Antioxidant Activity in Raw and Cooked Cactus Cladodes (Opuntia ficus-indica)

This study aims to investigate whether heat treatment applied to cactus cladodes influences the bioaccessibility of their (poly)phenolic compounds after simulated gastric and intestinal digestion. A total of 45 (poly)phenols were identified and quantified in raw and cooked cactus cladodes by ultra high performance liquid chromatography photodiode array detector high resolution mass spectrometry. Both flavonoids (60-68% total), mainly isorhamnetin derivatives, and phenolic acids (32-40%) with eucomic acids as the predominant ones significantly ( p < 0.05) increased with microwaving and griddling processes. After in vitro gastrointestinal digestion, 55-64% of the total (poly)phenols of cooked cactus cladodes remained bioaccessible versus 44% in raw samples. Furthermore, digestive conditions and enzymes degraded or retained more flavonoids (37-63% bioaccessibility) than phenolic acids (56-87% bioaccessibility). Microwaved cactus cladodes contributed the highest amount of (poy)phenols (143.54 mg/g dm) after gastrointestinal process, followed by griddled samples (133.98 mg/g dm), showing the highest antioxidant capacity. Additionally, gastrointestinal digestion induced isomerizations among the three stereoisomeric forms of piscidic and eucomic acids.